1949 3600 w/mid-50's 235 and SM420, points ignition.
Diagnosing a rough running engine here. And I did a search on coil specs and there's a lot of posts with conflicting numbers. Plain old Google is even more divergent!
My coil is a 12 month old NAPA 905 12V with internal resistor. It reads 2 ohms on the primary and 5,000 ohms on the secondary. A few months ago the condenser died and I put in one of those solid state ones from the members here. I get no visible spark on the spark tester, but I get enough spark to start (easily) and run the engine, but it runs super rough. Takes almost full throttle and liberal pumping to get it to idle (I did overhaul the Zenith 228 today, no change in symptoms).
The truck was running beautifully for a long time and then slowly started developing a rough stumble under load or acceleration. That stumble got worse and worse until it suddenly started running rough in all throttle settings and overheating. Since I had recently replaced the coil and condenser I assumed an overly lean carburetor (it was new, off-the-shelf from 1970 so I thought ethanol had finally gotten to it after a year), and rebuilt the carb but didn't see anything out of whack or dirty inside (float fine, jets clean, etc.).
I'm thinking the coil is bad, but with an online google search, 5,000 ohms on the secondary is mentioned as OK in a few places. More seem to say 10,000-20,000 ohms though, so I thought I'd check in with you guys!
The combo of rough running and overheating is perplexing.
